Low Cost Gear Fuel Pump

ABSTRACT

The present invention is directed to a gear pump having a housing ( 10 ′) with an interior pumping chamber ( 200 ) and an inlet ( 40 ′) to and outlet ( 42 ′) from the chamber, the outlet being spaced from the inlet. A pair of rotating gears ( 330,332 ) is located in the chamber, the gears including teeth which mesh during gear rotation. The gears are preferably powder metal construction and fixedly secured on a shaft ( 230,232 ) having an axis of rotation. A pair of one-piece bearings ( 210,212 ) is located in the chamber and journal one of first and second end portions of each shaft ( 320 ). The one-piece bearings provide precise alignment of the first and second end portions of the shafts and maintain the shafts in parallel relation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional PatentApplication Ser. No. 60/544,582 filed Feb. 13, 2004 and is incorporatedherein by reference.

BACKGROUND OF THE INVENTION

This present invention relates generally to gear pumps. Moreparticularly, it relates to an improved bearing and gear assemblyconstruction, particularly one used as a fuel pump, and methods ofmaking the same.

A typical gear fuel pump is a fixed displacement pumping device. Itreceives fuel from the fuel tank, pressurizes the fuel, and delivers thefuel at a higher pressure to the fuel nozzle via a fuel control forengine combustion. The gear pump generally includes a housing, such asan aluminum housing, having an interior pump chamber defined byparallel, intersecting, cylindrical bores. First and second gears,usually of similar configuration, are disposed in respective bores andthe gears mesh with each other in the area of intersection of the boresinside the housing. A first or drive gear has a splined drive shaft andas it rotates, the first gear drives a second gear, commonly called thedriven gear. As the gears rotate within the housing, fluid istransferred from an inlet to an outlet of the pump. The gears are highlystressed at high pressures and high loads. Gears of either spur orhelical configuration can be used; although spur gears are most common.The gears are driven to unmesh adjacent the inlet and convey the fluidaround the periphery of the bores to the region where the gears mesh.The meshing of the gears forces the fluid out of the pump chamber whereit exits the pump housing through the outlet.

Since the pressure of the fluid being pumped is greater at the outletthan at the inlet during pump operation, the pressure differential cancause leakage flow from the outlet to the inlet across the interfaces ofthe various components. This leakage flow lowers the efficiency of thepump. In some instances, there can be substantial variations in theleakage flow from one identically made pump to another. Since the volumepumped is a direct function of the volume displaced by the meshinggears, variation in depth of mesh gears will also greatly affectcapacity. Thus, it is important to provide precise alignment and meshingof the gears in order to improve pump efficiency.

Typically, four separate bearings are disposed in the bores and journalor support portions of the gear shafts. The bearings usually have agenerally cylindrical exterior configuration with facing and engagingflats along one portion of the periphery that align with region in whichthe gears mesh. The bearings are sized to fit the pump chamber. In theusual case, the bearings are manufactured paying close heed to thedesign dimension between the center of the flat and the diametricallyopposite side of the otherwise cylindrical bearing. In order to minimizeleakage paths, such bearings are made to form a tight fit withinrespective bores in the pump and not infrequently, due to tolerancevariations, good fitting cannot always be attained. Thus, it has beencustomary to, during the assembly process, shave material off of theflats of one or more of the bearings in the hope that a precise fit canbe achieved. Indeed, the bearings are designed to be shaved so as toaccommodate tolerance variation while attempting to maintain a tightfit.

However, in the shaving process, parallelism of the face of the flat tothe axial center line of the bearing may be lost, creating a leakagepath. Alternatively, the flatness of the face can be lost during theshaving process, again creating a leakage path across the flats. Theshaving process may also result in a loss of squareness orperpendicularity of the face of the flat to the end of the bearing whichin turn may not seal properly against the housing end wall, which mayprevent the bearing from moving properly in response to shaft deflectionduring operation, or may misalign the shafts. Shaving may also result ina changed depth of mesh of the gears journalled by the bearings, thusaltering the pump's capacity.

Another substantial factor resulting in the differing capacities inotherwise identical pumps is the fact that conventionally, each splineddrive shaft and corresponding gear are manufactured one-piece bar stockdriven gears where the bar portion (i.e. drive shaft) and gear areformed as a single, one-piece unit. As such, opposing end portions ofthe drive shaft are separately manufactured and may result in differingdiameters of the opposing end portions which impacts mating with thebearings.

Commonly assigned U.S. Pat. No. 6,042,352 is directed to a gear pump ofthe type for which the improved gear fuel pump was developed. Otherexisting gear pump designs are known in the art, including thefollowing: U.S. Pat. Nos. 4,682,938; 4,193,745; 4,097,206; 3,003,426;2,981,200; and 2,774,309.

In light of the foregoing, it is evident that there is a need for animproved gear pump that provides a solution to one or more of thedeficiencies in the art. It is still more clear that an improved gearpump, such as a fuel pump, providing a solution to each of the needsinadequately addressed by the prior art while providing a number ofheretofore unrealized advantages thereover would represent a markedadvance in the art.

BRIEF DESCRIPTION OF THE INVENTION

A new and improved gear fuel pump assembly is provided.

More particularly, and according to one embodiment of the presentinvention, the gear pump comprises a housing including an interiorpumping chamber and an inlet and outlet in spaced relation that eachcommunicate with the chamber. A pair of rotating gears is located in thechamber, each gear being fixedly secured on a respective shaft having anaxis of rotation. The gear teeth mesh to pressurize fluid pumped throughthe housing. A pair of one-piece bearings is located in the chamber onopposite ends of the gears and journal one of first and second endportions of each shaft. The one-piece bearings provide precise alignmentof the first and second the shafts and maintain the shafts in parallelrelation.

Preferably, the gears are formed from powder metal and secured onconstant diameter shafts. Each gear is keyed to one of the shafts so asto rotate therewith, and the dimensional tolerance between the shaft andgear provides for proper meshing of the gears if there is any slightmisalignment.

According to another embodiment of the present invention, a method ofassembling a gear pump is provided. The method comprises the steps ofproviding first and second shafts having substantially constantdiameters along their lengths. A gear is advanced over each shaft andsecured to each shaft. A one-piece bearing is then mounted on theshafts. The bearing and shafts with gears mounted thereon are installedinto a housing of a gear pump.

According to one aspect of the present invention, the one piece bearingsand the gears are made from powder metal. By using powder metaltechnology, the one-piece bearings and gears can be formed without therequirement of extensive additional machining.

A primary benefit of the present invention resides in the ability toprovide homogenous one-piece bearings which have a higher accuracy inalignment compared to conventional bearings.

Another benefit of the present invention resides in the ability toprovide powder metal components for a gear pump which last as long orlonger than components formed from conventional materials.

Still another benefit resides in the precise alignment associated withthe use of one-piece bearings.

A further benefit resides in the substantial savings associated withpowder metal components by reducing the extensive additionalmanufacturing steps associated with conventional bearings, gears andshafts.

Still other benefits and aspects of the invention will become apparentfrom a reading and understanding of the detailed description of thepreferred embodiments hereinbelow.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention may take physical form in certain parts andarrangements of parts, preferred embodiments of which will be describedin detail in this specification and illustrated in the accompanyingdrawings which form a part of the invention.

FIG. 1 is an exploded perspective view of a conventional gear pumpassembly.

FIG. 2 is a top plan view, partially broken away, of a cover plate andhousing of the conventional gear pump assembly of FIG. 1.

FIG. 3 is a sectional view taken approximately along line 3-3 in FIG. 2.

FIG. 4 is an exploded perspective view of a gear pump assembly accordingto the present invention.

FIG. 5 is a top plan view, partially broken away, of a cover plate andhousing of the gear pump assembly of FIG. 4.

FIG. 6 is a sectional view taken approximately along line 6-6 in FIG. 5.

FIG. 7 is a bottom plan view of a one-piece first bearing of the gearpump assembly of FIG. 4.

FIG. 8 is a sectional view taken approximately along line 7-7 in FIG. 7showing the first bearing.

FIG. 9 is a top plan view of the first bearing of the gear pump assemblyof FIG. 4.

FIG. 10 is a sectional view taken approximately along line 10-10 in FIG.9.

FIG. 11 is a top plan view of a one-piece second bearing of the gearpump assembly of FIG. 4.

FIG. 12 is a sectional view taken approximately along line 12-12 in FIG.11 showing the second bearing.

FIG. 13 is a bottom plan view of the second bearing of the gear pumpassembly of FIG. 4.

FIG. 14 is a sectional view taken approximately along line 14-14 in FIG.13.

FIG. 15 is a plan view of a first shaft of the gear pump assembly ofFIG. 4.

FIG. 16 is a sectional view taken approximately along line 16-16 in FIG.15.

FIG. 17 is a plan view of a second shaft of the gear pump assembly ofFIG. 4.

FIG. 18 is a side elevational view of the second shaft of FIG. 17.

FIG. 19 is a sectional view taken approximately along line 19-19 in FIG.18.

FIG. 20 is a top plan view of a gear of the gear pump assembly of FIG.4.

FIG. 21 is a sectional view taken approximately along line 21-21 in FIG.20.

DETAILED DESCRIPTION OF THE INVENTION

It should, of course, be understood that the description and drawingsherein are merely illustrative and that various modifications andchanges can be made in the structures disclosed without departing fromthe spirit of the invention. Like numerals refer to like partsthroughout the several views.

With reference to FIG. 1, a conventional gear pump assembly GP typicallyincludes a housing 10, generally made from aluminum, having end flanges12 and 14 and an end plate or lid 16 for sealing the housing. End flange12 includes a plurality of apertures 18 and the lid includescorresponding apertures 20 dimensioned to receive conventional fastenersF which secure the lid to the housing. As shown in FIGS. 1 and 2, theend flange 12 and the lid 16 are generally polygonal in cross-section,although, it should be appreciated by one skilled in the art that theend flange and lid can have other configurations depending on the use ofthe gear pump and/or the environment in which the pump is used. Thehousing further includes a recess 22 which receives a seal 24. Endflange 14 also includes a plurality of mounting apertures 26 formounting the gear pump GP to any source of rotational energy (notshown).

With reference to FIG. 2, the housing 10 includes a chamber 30, definedby two parallel, intersecting, cylindrical bores 32 and 34. The housing10 has an inlet 40 and an outlet 42. As shown in FIG. 1, the gear pumpGP further includes first and second gears 50, 52 disposed within thebores 32 and 34, respectively, so as to be meshed generally in theregion of a dotted line designated 54 in FIG. 3. The gear 50 isintegrally formed with a hollow drive shaft or journal 60 while the gear52 is integrally formed with a hollow driven shaft or journal 62.Typically, the shaft and gear are formed from stock material andmachined to the desired diameter of the shaft and the gear detail. Aswill be appreciated, a substantial amount of stock material is removedin this conventional manufacturing operation. Moreover, as noted in theBackground, there are problems associated with that conventionalarrangement.

The driven shaft 62 includes a splined internal surface (not shown)which is engaged by a splined end portion of a rotational shaft S whichis connected to the source of rotational energy. The rotational shaft Sextends through an opening (not shown) in the housing. An o-ring 68 anda shaft seal 70 are provided about the opening to prevent gear pumpexternal leakage. A seal 72 is normally coupled to the drive shaft.

Within the housing 10, both of the shafts 60, 62 have end portions 76which are supported or journalled in respective first and secondbearings 80, 82. The bearings 80, 82 are separately formed and generallycylindrical about the rotational axis of the shafts defined bycylindrical openings 84, 86. Each of the bearings is also provided withrespective flats 88, 90 on a portion of the circumference immediatelyadjacent the point 54 where the gears 50, 52 mesh. Each flat 88 onadjacent bearings 80 includes a hole or recess 92. The flats 88 faceeach other and engaged one another by a pin 94 received in the holes.Similarly, each flat 90 on adjacent bearings 82 include a hole or recess96 that receive a pin 98. The flats 88 and 90 are intended to be definedby planes parallel to the center line of the openings 84, 86.

Generally, the bearings are longitudinally fixed in the cylindricalbores 32 and 34 of the housing 10. However, a bottom surface 100 of eachbearing 82 includes a flange 102 having a plurality of openings (notshown) for receiving individual springs 104. As such, the pressurizedbearings are urged or biased in a longitudinal direction along the endportions 76 of the shafts 60, 62 in the cylindrical bores.

The fuel is pumped from the low pressure inlet side of the bearings 82to the high pressure discharge side of the bearings. The gears 50, 52,which are longitudinally received between the bearings 80, 82, rotateabout respective, parallel axes, and mesh together. Fluid is thus movedfrom the inlet around the outside of the gears 50, 52 to the outlet in amanner well known in the art.

As shown in FIGS. 1 and 2, the bearing arrangement and the cylindricalbores 32 and 34 of the housing 10 have a figure eight configuration. Inthe manufacture of the prior art bearings 80 and 82, the controlledtolerance is the distance from the flat 88 and 90 to a diametricallyopposite point on the periphery of the bearing. As described above, theflats 88 and 90 are typically shaved so as to allow the bearings 80 and82 to be fitted to in the gear pump housing 10. As such, the controlledtolerance is lost to some degree during the shaving process. Because theflats on bearings utilized in prior art gear pumps require shavingduring assembly, the loss of parallelism of the flat to the center lineof the bearing, the loss of flatness, or the loss of squareness of theflats 88.90 relative to respective top surfaces 110, 112 and bottomsurfaces 114, 100 of the bearings 80, 82 occurs. As a result, the gearpump GP may experience leakage or be less efficient than desired.

As briefly stated above, the gears 50, 52 are integrally formed with therespective shafts 60, 62. Each shaft and corresponding gear aremanufactured from a one-piece bar stock where the opposing end portions76 of the shaft and the gear are formed as a single unit. As such, theopposing end portions of the shaft are separately formed which mayresult in differing diameters of the opposing end portions. To correctthis dimensional difference, the diameter of the larger opposing endportion is typically ground down to match the diameter of the other endportion. However, this grinding process may also result in a loss ofsquareness or perpendicularity of the shafts 60 and 62 to the integralgears 50 and 52. This can effect the meshing of the gears, and since thevolume pumped is a direct function of the volume displaced by themeshing gears, can affect the capacity of the gear pump.

With reference now to FIG. 4, a gear pump according to the presentinvention is shown. Since much of the structure and function issubstantially identical, reference numerals with a single primed suffix(′) refer to like components (e.g., housing 10 is referred to byreference numeral 10′), and new numerals identify new components.Likewise, description of components that remain unchanged is notnecessary.

The gear pump assembly GP′ shown in FIGS. 4-6 includes the housing 10′having a chamber 200, defining a single cylindrical bore 202. Thehousing 10′ receives a pair of bearings 204, 206, each bearing being aone-piece bearing formed from powder metal. That is, the bearings aresubstantially homogenous components that do not have joint lines, i.e.,they are continuous, when compared to the two-piece bearing assembliesof the prior art. Each bearing preferably has a generally oblongcross-section. It will be appreciated that the periphery of each bearingmates with the similarly dimensioned bore 204 of the housing 10′.However, it should be appreciated by one skilled in the art that thebearings and corresponding bore can have other contours which wouldallow each bearing to be closely received within the chamber 200 ofhousing 10′.

With reference to FIGS. 8 through 10, the unitary bearing 204, which isgenerally longitudinally fixed in the housing, includes a first or topsurface 220, a second or bottom surface 222, and a pair of openings 224,226 having center axes coincident with axes of rotation of shafts orjournals 230, 232. The bearing further includes first and secondelongated sides 236, 238. The first elongated side is generally parallelto the second elongated side, and in the preferred arrangement theelongated sides are generally planar. Opposing ends 240, 242 have anarcuate contour, although as stated above, the ends can have otherconfigurations without departing from the scope and intent of thepresent invention.

With continued reference to FIG. 7, the bottom surface 222 of thebearing 210 includes a dam 250, an inlet face relief 252, and adischarge face relief 254. Thus, the bearing dam 250 is located betweenthe inlet face relief and the discharge face relief. The bearing damwall forms a sealed dam area between an inlet side 256 and an outletside 258, thus resulting in a low-pressure area on the inlet side 40′and high-pressure area on the outlet side 42′ of the gear pump GP′. Thebearing further includes a bleed hole 260 for bearing lubrication drain.As shown in FIG. 10, the bleed hole has a substantially constantdiameter along its length and intersects the dam area 250 in aperpendicular fashion.

With reference to FIGS. 11-14, the unitary bearing 212 includes a firstor top surface 270, a second or bottom surface 272, and a pair ofopenings 274, 276 having center axes coincident with the center axes ofthe openings 224, 226 of the bearing 210 and the axes of rotation of theshafts 230, 232. Similar to the bearing 210, the bearing 212 furtherincludes generally parallel first and second elongated sides 280, 282and a pair of arcuate ends 240 and 242.

Similar to the features of the bottom surface 222 of the bearing 210,the top surface 270 of the bearing 212 includes a dam 290, an inlet facerelief 292, and a discharge face relief 294, the bearing dam wallforming a sealed dam area between an inlet side 296 and an outlet side298, thus also resulting in a low-pressure area on the inlet side 40′and high-pressure area on the outlet side 42′ of the gear pump GP′. Thebearing further includes a blind hole 300 for the retention of anenergized spring 302.

As seen in FIG. 14, the bottom surface 272 of the bearing 212 includes aflange 310. A seal 312 can be provided about the flange.

A pair of gears 330, 332 are longitudinally received on the shafts 230,232 between the bearings 210, 212 (FIG. 4). With reference to FIGS. 15through 19, each shaft 230, 232 includes an axial recess 340 and firstand second spaced, circumferential grooves 342, 344 extending radiallyinward from the outer periphery 346 of each shaft for receivingretaining rings or snap rings 350 (FIG. 4). The snap rings fixedlysecure the gears 330, 332 on the shafts 230, 232 and precludelongitudinal movement of the gears relative to the respective shaft.

Each shaft 230, 232 is generally hollow and has a substantially constantdiameter along its lengths. As shown in FIG. 16, shaft 232 also has aconstant inner diameter. As shown in FIGS. 18 and 19, a portion 352 ofan inner surface 350 of the drive shaft 230 is splined. The splinedportion is engaged by a splined portion of a rotational shaft S′ whichis connected to a source of rotational energy. The rotational shaft S′extends through an opening (not shown) in the housing.

The shafts 230 and 232 are formed by conventional metal manufacturing.Each gear 330 and 332 (FIGS. 20-21) on the other hand is manufacturedfrom powdered metal and includes an opening 360 adapted for receipt overone of the shafts 230, 232. The dimensional tolerance between the outerdiameter of the shaft and the diameter of opening 360 of the gearprovides some self alignment of the teeth 362 of the gears as the gearsmesh if the gears/shafts are not precisely aligned. Each gear is securedgenerally perpendicular on the respective shaft. Each gear furtherincludes an axial groove 364. The axial recess 340 of the shafts and theaxial groove 364 of the gear are dimensioned to receive a pin 370 thatfixes or keys the gear to the shaft.

Generally, to assemble the gear pump GP′, a first snap ring 350 issecured in one of the first and second grooves 342, 344 of the shafts230, 232. The snap ring prevents axial movement of the gears on theshafts. The pin 370 is placed in the axial recess 340. The gears 330,332 are then advanced over each shaft in such a manner that the axialgroove is aligned with the pin and the axial recess. Thus, the axialrecess and groove together form a housing for the pin, the pinpreventing rotation of the gears on the respective shafts. A second snapring 350 is secured in the other groove thereby longitudinally oraxially securing the gear to each shaft. The one-piece continuousbearing 212 is then installed in the chamber 202 of the housing 10′. Theassembled shafts (i.e. shafts with gears mounted thereon) are mounted onthe bearing, shaft portions 320 being journalled in the openings 274,276 of the bearing. The one-piece bearing 210 is then mounted on theassembled shafts, shaft portions 320 being journalled in the openings224, 226 of the bearing. Thus, the one-piece bearings provide precisealignment of the shafts and maintain the shafts in parallel relation inthe housing. The lid 16′ is then secured to the housing via theconventional fasteners F′.

Accordingly, the present invention provides a gear pump having powdermetal components with distinct advantages over the conventionalcomponents. In addition to the uniqueness of using powdered metaltechnology to make the bearings 210 and 212, the continuousconfiguration of the bearing provides a higher accuracy in alignment byavoidance of the connecting separate bearing 80, 82 of the prior art.Thus, it is possible to precisely align the center axes of the openingsfor the bearings.

Moreover, the one-piece bearings 210, 212 in the preferred embodimentare a straight line design, i.e., across the top and bottom surfaces ofthe bearing, whereas, the conventional bearing 80, 82, when connected,have a figure eight design. By incorporating the straight line design, amore precise and easier alignment of the bearings 210, 212 into thechamber 200 of the housing 10′ can be achieved compared to theconventional figure eight design.

The one-piece bearing 210, 212 also allows for greater control of theopenings in centerline-to-centerline positioning where the control maybe as much as plus or minus one hundredth millimeter. However, thetwo-piece figure of eight design generally needs to be machine leveledto obtain that exactness, which is very time consuming. Further, sincethe separate bearings 80, 82 are connected, it is possible thatseparation of the two piece bearing may occur thereby not allowingfunctional operation. On the other hand, because the bearings 210, 212have a unitary design, they cannot separate during operation of the gearpump GP′.

Cost benefits over the above described prior art design approach ascompared to the low cost powdered metal design approach of the presentapplication are set forth, in one example, in the following Table:

Conventional Design Low Cost Powder Metal Feature Approach (P/M) DesignApproach Gear Gear and journal one piece Gear blank and journalfabrication formed separately Gear Rough machined individually PrecisionCarbide Tooling Teeth and final ground. Part fabricated once, net shapeinspection required. High formed, millions can be Cost (about $800-$2500per pressed without changing set). the tooling. Random sampling isrequired. High initial tooling cost but very low formed piece part cost(approximately $25-$30 each). Gear Cut from a circular bar Separatedcenter-less Journal stock together with the ground. One journal, nogear. Both sides of matching problem. Key way journal size to be isneeded to drive the gear matched precisely. blank. Retaining rings toIntegrated with gear, one position the gear blank piece construction.(approximately $25-$30 each). Gear Matching to about .0002 Dozen can beground to the Width inch, large pool of same height at once, no Matchinginventory is required for matching is required. Two matching. Parallelto sides will be automatically within about .0002 inch. parallel. ThrustSpecial super finishing Not required, as ground. Face operation. FinishDe- Required, time consuming. Tumble finish, a very burring simpleoperation. Drive Splined shaft, costly. Hex Drive, low cost. Total Veryhigh approximately 20% of Cost conventional cost Pres- Two separatedparts One piece construction surized Bearing Drive Fabricatedindividually. Designed for Powdered Bearing Final lapping at pump Metalapplication. One assembly. single piece. Net shape High precisionmachining bronze powdered metal. required. Minimum machining DrivenFabricated individually, required. One time initial Bearing differentfrom drive tooling cost, very low per bearing. Final lapping pieceformed part cost at pump assembly. (approximately $3.00-$5.00 Relativelyhigh cost. each). Loading Generally 12 for pressurized One Springbearings Fixed Two fixed and two One piece construction Bearingpressurized Drive Fabricated individually. One single piece. Net shapeFinal lapping at pump bronze powdered metal. assembly Minimum machiningis Driven Fabricated individually, required. No matching is differentfrom drive bearing. needed. One time initial Matching in height istooling cost, very low per required. Final lapping at piece formed partcost. pump assembly. Relatively (approximately $2.00-$4.00 high cost.each). Total High approximately 25% of Cost conventional design. DriveInput and Output splines Hex shaft cut from standard Shaft stock TotalHigh approximately 10% of Cost conventional design. Total Very Highapproximately 30%-40% of Gear the conventional design Pump Ass'y Cost

It is to be understood the above percentages and dollar figures aresimply estimates and the values may, depending on the implementation, bedifferent from those cited.

Accordingly, using powder metal to manufacture components for the gearpump GP′ result in a much-improved manufacturing cost structure for gearpump fabrication and assembly. This is true since the gears, bearingsand shafts constitute the majority of the fuel pump components.

The exemplary embodiment has been described with reference to thepreferred embodiments. Obviously, modifications and alterations willoccur to others upon reading and understanding the preceding detaileddescription. It is intended that the exemplary embodiment be construedas including all such modifications and alterations insofar as they comewithin the scope of the appended claims or the equivalents thereof.

1. A gear pump comprising: a housing including an interior pumpingchamber; an inlet to the chamber; an outlet from the chamber and spacedfrom the inlet; a pair of rotating gears in the chamber, the gearsincluding teeth which mesh during gear rotation, each gear being fixedlysecured on a shaft having an axis of rotation; and a pair of one-piecebearings located in the chamber and journaling one of first and secondend portions of each shaft, the one-piece bearings providing precisealignment of the first and second end portions of the shafts andmaintaining the shafts in parallel relation; wherein the one-piecebearings are manufactured from powdered metal whereby each bearing ishomogenous and has a substantially uniform composition throughout. 2.(canceled)
 3. The gear pump of claim 1 wherein each one-piece bearinghas a generally oblong cross-section.
 4. The gear pump of claim 1wherein each one-piece bearing includes: a top surface, a bottomsurface, a pair of openings having center axes coincident with the axesof rotation of the shafts, and first and second elongated sides,opposing ends of the first side being joined to corresponding opposingends of the second side by a pair of arcuate ends.
 5. The gear pump ofclaim 4 wherein the first elongated side is parallel to the secondelongated side.
 6. The gear pump of claim 4 wherein the first and secondelongated sides are generally planar.
 7. The gear pump of claim 1wherein each gear is manufactured from powdered metal.
 8. The gear pumpof claim 7 wherein each gear includes an opening adapted to receive theshaft thereby allowing for self alignment of the teeth of the gears asthe gears mesh.
 9. The gear pump of claim 1 wherein each shaft includesan axial recess and each gear includes an axial groove dimensioned toreceive a pin for preventing rotation of the gears on the respectiveshafts.
 10. The gear pump of claim 1 wherein each shaft includes firstand second grooves extending radially about the periphery of each shaftfor receiving associated snap rings.
 11. The gear pump of claim 1wherein each gear is secured perpendicularly on each shaft.
 12. A methodof assembling a gear pump comprising the steps of: providing first andsecond shafts having substantially constant diameter along theirlengths; forming a bearing from powder metal whereby the bearing ishomogenous; advancing a gear over each shaft; securing the gear to eachshaft; mounting the bearing on the shafts; installing the bearing andshafts with gears mounted thereon into a housing of a gear pump.
 13. Themethod of claim 12 comprising the further steps of preventing rotationof the gear relative to each shaft.
 14. The method of claim 12comprising the further steps of providing one-piece continuous bearingson each end of the shafts.
 15. The method of claim 14 comprising thefurther steps of journaling each shaft in the one-piece bearings, theone-piece bearings providing precise alignment of the shafts.
 16. Themethod of claim 12 comprising the further steps of forming each gearfrom powder metal whereby each gear has a substantially uniformcomposition throughout.
 17. (canceled)